1. Field of the Invention
This invention relates generally to micromachining methods and, more particularly, to a method of fabricating a micromachined current switch with moving contacts which are sealed and reinforced with a polyimide material.
2. Description of the Related Art
When fabricating micromechanical structures, micromachined moving parts usually undergo a processing step in which they are released for further processing by etching away either a mold or a sacrificial release layer. For example, commonly assigned Ghezzo et al., "Micromechanical Moving Structures Including Multiple Contact Switching System, and Micromachining Methods Therefor," U.S. application Ser. No. 08/000,172, filed Jan. 4, 1993, describes one method for using a copper release layer. The resulting moving parts can be fragile because small metal hinges hold contact bridges in position. Consequently, processing steps which require forceful flows of liquid or air can damage these parts.
Reinforcement of the hinges of micromachined moving parts not only would serve to protect these moving parts during fabrication but would also be beneficial during normal operation of the parts. Any such reinforcement, however, must be flexible enough so as to not interfere with the movement of the part.
When switches are batch-fabricated on a substrate, they need to be separated or cut into individual switches after fabrication. A simple method of cutting a substrate is to use a standard wafer saw. A seal is needed to protect the switches during sawing because wafer particles can interfere with switch movement during operation, and forced liquids which are used to cool the saw can damage the contact bridges.